Overlap joint flex circuit board mating

ABSTRACT

An interconnection for flex circuit boards used, for instance, in a quantum computing system are provided. In one example, the interconnection can include a first flex circuit board having a first side and a second side opposite the first side. The interconnection can include a second flex circuit board having a third side and a fourth side opposite the third side. The first flex circuit board and the second flex circuit board are physically coupled together in an overlap joint in which a portion of the second side for the first flex circuit board overlaps a portion of the third side of the flex circuit board. The interconnection can include a signal pad structure positioned in the overlap joint that electrically couples a first via in the first flex circuit board and a second via in the second flex circuit board.

PRIORITY CLAIM

The present application claims the benefit of priority of U.S.Provisional Application Ser. No. 63/079,274, filed Sep. 16, 2020, titledOverlap Joint Flex Circuit Board Interconnection, which is incorporatedherein by reference.

FIELD

The present disclosure relates generally to interconnections for, forinstance, classical or quantum computing systems.

BACKGROUND

Quantum computing is a computing method that takes advantage of quantumeffects, such as superposition of basis states and entanglement, toperform certain computations more efficiently than a classical digitalcomputer. In contrast to a digital computer, which stores andmanipulates information in the form of bits, e.g., a “1” or “0,” quantumcomputing systems can manipulate information using quantum bits(“qubits”). A qubit can refer to a quantum device that enables thesuperposition of multiple states, e.g., data in both the “0” and “1”state, and/or to the superposition of data, itself, in the multiplestates. In accordance with conventional terminology, the superpositionof a “0” and “1” state in a quantum system may be represented, e.g., asa |0

+b|1

. The “0” and “1” states of a digital computer are analogous to the |0

and |1

basis states, respectively of a qubit.

SUMMARY

Aspects and advantages of embodiments of the present disclosure will beset forth in part in the following description, or can be learned fromthe description, or can be learned through practice of the embodiments.

One example aspect of the present disclosure is directed to aninterconnection for connecting a plurality of flex circuit boards. Theinterconnection can include a first flex circuit board having a firstside and a second side opposite the first side. The interconnection caninclude a second flex circuit board having a third side and a fourthside opposite the third side. The first flex circuit board and thesecond flex circuit board are physically coupled together in an overlapjoint in which a portion of the second side for the first flex circuitboard overlaps a portion of the third side of the flex circuit board.The interconnection can include a signal pad structure positioned in theoverlap joint that electrically couples a first via in the first flexcircuit board and a second via in the second flex circuit board.

These and other features, aspects, and advantages of various embodimentsof the present disclosure will become better understood with referenceto the following description and appended claims. The accompanyingdrawings, which are incorporated in and constitute a part of thisspecification, illustrate example embodiments of the present disclosureand, together with the description, serve to explain the relatedprinciples.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed discussion of embodiments directed to one of ordinary skill inthe art is set forth in the specification, which refers to the appendedfigures, in which:

FIG. 1 depicts a diagram of an example flex circuit boardinterconnection according to example aspects of the present disclosure.

FIG. 2 depicts an illustration showing a top view of an example flexcircuit interconnection according to example aspects of the presentdisclosure.

FIG. 3 depicts an illustration showing example solder placement of anexample interconnection according to example aspects of the presentdisclosure.

FIG. 4 depicts a flow diagram of an example method for producing aninterconnection according to example aspects of the present disclosure.

FIG. 5 depicts a quantum computing system according to exampleembodiments of the present disclosure.

FIG. 6 depicts a quantum computing system according to exampleembodiments of the present disclosure.

DETAILED DESCRIPTION

Example aspects of the present disclosure are directed to making andusing specialized overlap joint interconnections that can connectvarious types of circuit boards including, but not limited to, flexibleand semi-flexible circuit boards used in traditional computing systems,quantum computing systems, and other types of electronics (e.g.,automobiles, aircraft, satellites, medical devices, smartphones,wearable devices, etc.). A circuit board generally refers to a piece ofmaterial with printed or integrated circuits, which is used to connectelectronic components and devices. Flex circuit boards can includecircuit boards that provide at least some structural flexibility inwhole or in part.

Flex circuit boards may be used in a variety of electronics, forexample, where flexibility and space savings would be difficult orimpossible to achieve with rigid circuit boards. While flex circuitboards can have advantages over rigid circuit boards, connecting flexcircuit boards can be problematic. For example, the inherent pliabilityof flex circuit boards presents an increased risk of damage duringhandling and use due to movement and reduced structural support. Inaddition, the repair or replacement of damaged flex circuit boards canbe inconvenient and expensive. As such, the present disclosure describesnew and improved ways of making and using overlap joints thatinterconnect flex circuit board.

According to example aspects of the present disclosure, an overlapinterconnection for interconnecting multiple circuit boards, such asflex circuit boards can include, for instance, a first flex circuitboard having a first side and a second side opposite the first side. Theinterconnection can include a second flex circuit board having a thirdside and a fourth side opposite the third side. The first flex circuitboard and the second flex circuit board can be physically coupled toeach other in an overlap joint in which a portion of the second side ofthe first flex circuit board overlaps a portion of the third side of theflex circuit board.

The first flex circuit board can include a first signal line, a firstdielectric layer, and a first via. The first via can extend through thefirst dielectric layer at least from the first signal line to the secondside of the first flex circuit board. The second flex circuit board caninclude a second signal line, a second dielectric layer, and a secondvia. The second via can extend through the second dielectric layer atleast from the second signal line to the third side of the second flexcircuit board. The interconnection further includes a signal padstructure positioned in the overlap joint between the second side of thefirst flex circuit board and the third side of the second flex circuitboard and electrically coupled to the first via and the second via.

Example aspects of the present disclosure also are directed to methodsof producing wiring structures for interconnecting various types ofcircuit boards in, for example, computing systems, quantum computingsystems, and different types of electronics (e.g., automobiles,aircraft, satellites, medical devices, smartphones, wearable devices,etc.). A method may include, for example, obtaining a first circuitboard, obtaining a second circuit board, aligning the first circuitboard and the second circuit board such that a signal pad structure ispositioned in an overlap joint between the second side of the firstcircuit board and the third side of the second circuit board, andcoupling at least a first via in the first flex circuit board and viasecond via in the second flex circuit board at the signal pad structure.

Aspects of the present disclosure provide a number of technical effectsand benefits. For instance, the various examples of the interconnectionsdescribed in the present disclosure provide increased reinforcement anddurability when interconnecting flex circuit boards, which may flex,bend, and contort to fit a final assembly. For example, the flex circuitboard interconnections described herein protect against and reduce thelikelihood of damage during installation, deployment, use, andmaintenance of various types of traditional computing systems, quantumcomputing systems, consumer devices, industrial equipment, aerospaceequipment, etc. As such, these new and improved flex circuit boardinterconnections provide greater dependability and resiliency whencompared to traditional interconnections, thereby reducing damage,repair, replacement, downtime, and costs associated with various typesof systems, devices, and equipment using flex circuit boards.

As used herein, a “flex circuit board” refers to a board including atleast one generally planar substrate (e.g., layered substrates) or othersupport on which the one or more signal lines are formed or otherwisedisposed and having flexibility in at least one plane. Flexibilityrefers to the ability to be deformed without breaking. For example, arectangular flex circuit board may be flexible along the largest surfaceof the rectangular flex circuit board. A rectangular flex circuit boardmay be flexible and/or rigid along at least a portion of its edges. Theflexibility may be achieved as a property of material(s) from which theflex circuit board and/or layers of the flex circuit board is/are formed(e.g., metals, such as copper, copper alloys, niobium, aluminum, etc.,dielectric materials, nonmetals, polymers, rubbers, etc.), achieved byhinging and/or segmenting of the flex circuit board (e.g., hingingand/or segmenting a rigid portion), and/or in any other suitable manner.The substrate(s) may be strictly planar (e.g., having a substantiallylinear cross-section across a length and width) and/or may be generallyplanar in that the substrate(s) bend, wrinkle, or are otherwisenon-linear in at least one cross-section but generally represent a shapehaving a depth significantly less than (e.g., less than about 10% of) alength and width.

As used herein, the use of the term “about” or “approximately” inconjunction with a stated numerical value is intended to refer to within10% of the stated numerical value.

With reference now to the Figures, example embodiments of the presentdisclosure will be discussed in further detail. Aspects of the presentdisclosure are discussed with referenced to interconnections for flexcircuit boards in quantum computing systems for purposes of illustrationand discussion. Those of ordinary skill in the art, using thedisclosures provided herein, will understand that the interconnectioncan be used in other applications without deviating from the scope ofthe present disclosure.

FIG. 1 depicts a cross-sectional view of an example overlap jointflex-flex interconnect 100 according to example embodiments of thepresent disclosure. The overlap joint interconnect 100 can be used forinterconnecting multiple flex circuit boards. The overlap jointinterconnect 100 can be made between a first flex circuit board 110 anda second flex circuit board 120. The first flex circuit board 110 caninclude ground layer(s) 112, dielectric layer(s) 114, and/or signalline(s) 116. Similarly, the second flex circuit board 120 can includeground layer(s) 122, dielectric layer(s) 124, and/or signal line(s) 126.The first flex circuit board 110 and the second flex circuit board 120may include the same materials and/or different materials.

The first flex circuit board 110 can include at least one via 118extending through the dielectric layer 114 from the signal line 116 to asecond side of the first flex circuit board (e.g., a side having theground layer 112). For example, the via 118 can be a same material asthe signal line 116 (e.g., superconducting material) and/or may bedifferent material. The via 118 can be surrounded by gap 119. Forexample, gap 119 may be circular on a surface having the ground layer112. In some embodiments, such as illustrated in FIG. 1 , the via 118can extend through both dielectric layers 114. For example, the via 118can be a so-called “through via” that extends from a first surface ofthe first flex circuit board 110 to a second surface of the first flexcircuit board 110. Additionally and/or alternatively, the via 118 can bea so-called “blind via” that extends from the signal line 116 to onlyone side of the first flex circuit board 110 (e.g., to signal pad 132).

The second flex circuit board 120 can additionally include at least onevia 128 extending through the dielectric layer 124 from the signal line126 to a second side of the second flex circuit board (e.g., a sidehaving the ground layer 122). For example, the via 128 can be a samematerial as the signal line 126 (e.g., superconducting material) and/ormay be different material. The via 128 can be surrounded by gap 129. Forexample, gap 129 may be circular on a surface having the ground layer122. In some embodiments, the via 128 can extend through both dielectriclayers 124. In some embodiments, such as illustrated in FIG. 1 , the via128 can extend through both dielectric layers 124. For example, the via128 can be a so-called “through via” that extends from a first surfaceof the second flex circuit board 120 to a second surface of the secondflex circuit board 120. Additionally and/or alternatively, the via 128can be a so-called “blind via” that extends from the signal line 126 toonly one side of the second flex circuit board 120 (e.g., to signal pad132).

The overlap joint flex-flex interconnect 100 can include overlap joint130. For instance, overlap joint 130 can be formed at an overlap offirst flex circuit board 110 and second flex circuit board 120. In someembodiments, the first flex circuit board 120 and the second flexcircuit board 120 can overlap by about 3 mm to about 7 mm.

The overlap joint 130 can include at least signal pad 132. Signal pad132 can be configured to couple signal line 116 (e.g., by via 118) ofthe first flex circuit board 110 to signal line 126 (e.g., by via 128)of the second flex circuit board 120. The signal pad 132 can facilitatesignal transfer between the first flex circuit board 110 and the secondflex circuit board 120. Additionally, the overlap joint 130 can includeone or more ground pads 134. A ground pad 134 can couple a ground layer112 of the first flex circuit board 110 to a mated ground layer 122 ofthe second flex circuit board 122. For example, the ground pad 134 canplace the ground layers 112 and 122 in electrical communication. One ormore gaps 136 can be provided between the signal pad 132 and the groundpad(s) 134 to isolate the signal pad 132 from the ground pad(s) 134. Insome embodiments, the signal pad 132, ground pad 134, and/or gaps 136can be designed for impedance matching for transmitted signals.

FIG. 2 depicts an illustration showing a top view of an example flexcircuit board 200 to be used in overlap joint interconnection accordingto example aspects of the present disclosure. The flex circuit board 200can include a ground layer(s) 112, signal line(s) 116, via(s) 118,circular signal pad(s) 132, and ground pads 134 surrounding the circularsignal pad(s) 132. The top view illustration shows a series of signallines 116, vias 118, and circular signal pads 132 that are allsurrounded by the ground layer(s) 112. Circular signal pad(s) 132 canhave a circular structure. The vias 118 can be connected to the signallines 116 such that a signal passing through the signal lines 116 can bepropagated through the vias 118. More particularly, the exposed signalpad(s) 132 and ground pads 134 can be coupled to a mirror-matched mateof a second flex circuit board to form the overlap interconnection. Moreparticularly, the first flex circuit board can mirror the second flexcircuit board.

FIG. 3 depicts a close up view of an example via 118 associated with asignal line 116 of a flex circuit board 300 to be used in an overlapjoint interconnection according to example embodiments of the presentdisclosure. As shown, the flex circuit board 300 includes groundlayer(s) 112, signal line 116, via 118, a circular signal pad 132, andground pads 134 disposed at least partially around the circular signalpad 134. A gap 136 is formed between the circular signal pad 132 and theground layer 112. Solder 302 can be used to couple ground pads 134together and to matching ground pads of a flex circuit board to beinterconnected with flex circuit board 300 in an overlap jointinterconnection. Similarly, solder 304 can be used to couple circularsignal pad 132 to a matching signal pad of a flex circuit board to beinterconnected with the flex circuit board 300 in an overlap connection.

FIG. 4 depicts a flow diagram of an example method 400 for producing aninterconnection according to examples of the present disclosure.Although FIG. 4 depicts steps performed in a particular order forpurposes of illustration and discussion as an example, the methods ofthe present disclosure are not limited to the particularly illustratedorder or arrangement. As such, the various steps of the method 400 canbe omitted, rearranged, combined, and/or adapted in various ways withoutdeviating from the scope of the present disclosure.

At 402, a first flex circuit board is obtained. For example, first flexcircuit board may comprise first and second ground layers, first andsecond dielectric layers, and/or signal line(s). In some examples, firstflex circuit board can include at least one via extending through thedielectric layer from the signal line (e.g., to a second side of thefirst flex circuit board). For example, the via can be a same materialas the signal line (e.g., superconducting material) and/or may bedifferent material.

At 404, a second flex circuit board is obtained. For example, the secondflex circuit board respectively may comprise a first and second groundlayers, a first and second dielectric layers, and/or signal line(s). Insome examples, second flex circuit board can include at least one viaextending through the dielectric layer from the signal line (e.g., to asecond side of the second flex circuit board). For example, the via canbe a same material as the signal line (e.g., superconducting material)and/or may be different material.

At 406, the first flex circuit board and the second flex circuit boardare aligned such that a signal pad structure is positioned in an overlapjoint. In an example, a side or edge of a first flex circuit board isaligned with a side or edge of a second flex circuit board so that thesignal pad structures face one another, for example, from opposite sidesin a symmetrical or substantially symmetrical manner. In some examples,heated assembly jigs may be used, for example to align first flexcircuit board with second flex circuit board and to perform varioussteps of assembling flex circuit overlap joint.

In some examples, first flex circuit board and second flex circuit boardare laterally aligned and converge or overlap one another based on analignment that forms an overlap between the signal pad structures ofdifferent flex circuit boards. In some examples, exposed via(s) of firstflex circuit board are in contact with exposed via(s) of second flexcircuit board.

At 408, the first via and the second via are coupled to one another inthe overlap joint by the signal pad structure. In an example, the firstand second via are coupled by solder. The solder connection can createconnectivity between the first via and the second via. In addition, theground layer of the first flex circuit board can be coupled to theground layer of the second flex circuit board by coupling ground pad(s).In an example, the ground pads are coupled via a solder connection.

FIG. 5 depicts a block diagram of an example quantum computing systemaccording to examples of the present disclosure. Quantum computingsystem 500 is an example of a system implemented as a classical orquantum computer program on one or more classical computers or quantumcomputing devices in one or more locations, in which the systems,components, and techniques described in the present disclosure can beimplemented. Quantum computing system 500 is an example that can be usedto implement aspects of the present disclosure. Those of ordinary skillin the art, using the examples provided herein, will understand thatother quantum computing structures or systems can be used withoutdeviating from the scope of the present disclosure.

Quantum computing system 500 includes quantum hardware 502 in datacommunication with one or more classical processor(s) 504. For instance,quantum hardware 502 can represent and/or manipulate information usingqubits. A qubit can be or include any suitable quantum device thatenables the superposition of multiple states, e.g., data in both the “0”and “1” state. As one example, a qubit can be or include a unit ofsuperconducting material, such as superconducting material that achievessuperconductivity in temperatures below about 10 mK.

Quantum hardware 502 can include components for performing quantumcomputation. For example, quantum hardware 502 can include a quantumsystem 510, control device(s) 512, and readout device(s) (e.g., readoutresonator(s) 514). Quantum system 510 can include one or moremulti-level quantum subsystems, such as a register of qubits. In someimplementations, the multi-level quantum subsystems can includesuperconducting qubits, such as flux qubits, charge qubits, transmonqubits, gmon qubits, etc.

Classical processor(s) 504 can be binary processors, such as processorsthat operate on data represented as a plurality of bits. As one example,bits can be represented by a voltage differential between a low voltage(e.g., 0V) and a high voltage (e.g., 5V) at a point of reference, suchas a memory cell, circuit node, etc. The low voltage can be associatedwith a “0” state and the high voltage can be associated with a “1”state. Classical processor(s) 504 can be configured to, in addition toany other suitable function(s) of classical processor(s) 504, controlquantum hardware 502. For instance, classical processor(s) 504 can becoupled to quantum hardware 502 (e.g., by signal lines) and/orconfigured to send control signals to perform quantum operations usingquantum hardware 502. As one example, classical processor(s) 504 can beconfigured to send control signals that implement quantum gateoperations at quantum hardware 502 (e.g., by control device(s) 512).Additionally and/or alternatively, classical processor(s) 504 can beconfigured to send control signals that cause quantum hardware 502 toperform quantum state measurements and/or provide the quantum statemeasurements to classical processor(s) 504 (e.g., by readout device(s)such as readout resonator(s) 514). For example, classical processor(s)504 can receive measurements of the quantum system 510 that can beinterpretable by classical processor(s) 504.

The type of multi-level quantum subsystems that quantum computing system500 utilizes may vary. For example, in some cases it may be convenientto include one or more readout device(s) (e.g., readout resonator(s)514) attached to one or more superconducting qubits, e.g., transmon,flux, gmon, xmon, or other qubits.

Quantum circuits may be constructed and applied to the register ofqubits included in the quantum system 510 via multiple signal lines(e.g., signal line(s) 116, 126 of FIG. 1 ) that are coupled to one ormore control devices 512. Example control devices 512 that operate onthe register of qubits can be used to implement quantum logic gates orcircuits of quantum logic gates, e.g., Hadamard gates, controlled-NOT(CNOT) gates, controlled-phase gates, T gates, multi-qubit quantumgates, coupler quantum gates, etc. One or more control devices 512 maybe configured to operate on quantum system 510 through one or morerespective control parameters (e.g., one or more physical controlparameters 506). For example, in some implementations, the multi-levelquantum subsystems may be superconducting qubits and control devices 512may be configured to provide control pulses to control lines (e.g.,signal line(s) 116, 126 of FIG. 1 ) to generate magnetic fields toadjust a frequency of the qubits.

Quantum hardware 502 may further include readout devices (e.g., readoutresonators 514). Measurement results 508 obtained via measurementdevices may be provided to the classical processors 504 for processingand analyzing. In some examples, quantum hardware 502 may include aquantum circuit and control device(s) 512, and readout devices mayimplement one or more quantum logic gates that operate on quantum system510 through physical control parameters (e.g., microwave pulse) that aresent through wires included in quantum hardware 502. Further examples ofcontrol devices include arbitrary waveform generators, wherein a DACcreates the signal.

Readout device(s) (e.g., readout resonator(s) 514) may be configured toperform quantum measurements on quantum system 510 and send (e.g., bysignal line(s) 116, 126 of FIG. 1 ) measurement results 508 to classicalprocessor(s) 504. In addition, quantum hardware 502 may be configured toreceive data (e.g., by signal line(s) 116, 126 of FIG. 1 ) specifyingvalues of physical control parameter(s) 506 from classical processor(s)504. Quantum hardware 502 may use the received values of physicalcontrol parameter(s) 506 to update the action of control device(s) 512and readout devices(s) (e.g., readout resonator(s) 514) on quantumsystem 510. For example, quantum hardware 502 may receive dataspecifying new values representing voltage strengths of one or more DACsincluded in control device(s) 512 and may update the action of the DACson quantum system 510 accordingly. Classical processor(s) 504 may beconfigured to initialize quantum system 510 in an initial quantum state,for example, by sending data to quantum hardware 502 specifying aninitial set of parameters 506.

Readout device(s) (e.g., readout resonator(s) 514) can take advantage ofa difference in the impedance for the |0

and |1

states of an element of quantum system 510, such as a qubit, to measurethe state of the element (e.g., the qubit). For example, the resonancefrequency of a readout resonator 514 can take on different values when aqubit is in the state |0

or the state |1

, due to the nonlinearity of the qubit. Therefore, a microwave pulsereflected from a readout device (e.g., readout resonator 514) carries anamplitude and phase shift that depends on the qubit state. In someexamples, a Purcell filter can be used in conjunction with readoutdevice(s) (e.g., readout resonator(s) 514) to impede microwavepropagation at the qubit frequency.

Quantum computing system 500 includes control device(s) 512. Controldevice(s) 512 can operate the quantum hardware 502. For example, controldevice(s) 512 can include a waveform generator configured to generatecontrol pulses according to example aspects of the present disclosure.

In some examples, control device(s) 512 may include a data processingapparatus and associated memory. The memory may include a computerprogram having instructions that, when executed by a data processingapparatus, cause the data processing apparatus to perform one or moreoperations, such as applying a control signal to a qubit and/or to atunable coupler.

Quantum hardware 502, such as, but not limited to, quantum system 510,control device(s) 512, readout device(s) 514, and/or any other suitablecomponents of quantum hardware 502, can be located within a cryogeniccooling system (not shown). Additionally and/or alternatively, classicalprocessor(s) 504 can be located outside a cryogenic cooling system. Forinstance, a cryogenic cooling system can be configured to cool quantumhardware 502. Additionally and/or alternatively, classical processor(s)504 are not cooled by cryogenic cooling system. For instance, classicalprocessor(s) 504 can operate at temperatures around room temperature(e.g., around 300 Kelvin) and/or temperatures around about 100 Kelvin,whereas quantum hardware 502 can operate at temperatures around absolutezero (e.g., less than about 1 Kelvin), which may require cooling by acryogenic cooling system to operate effectively.

Quantum computing system 500 can include signal lines (not shown). Thesignal lines can couple classical processor(s) 504 to quantum hardware502. For instance, as classical processor(s) 504 and quantum hardware502 can be in signal communication, such as to transmit parameter(s) 506and/or measurement result(s) 508 and/or any other suitable signals,classical processor(s) 504 can be coupled to quantum hardware 502 bysignal lines. For instance, signal lines can be or can include anysuitable physical communicative coupling(s) (e.g., one or more wires)configured to couple quantum hardware 502 and classical processor(s)504. Generally, signal lines may include physical connections to allowfor faster and/or more robust communication between quantum hardware 502and classical processor(s) 504. Further, signal lines can be at leastpartially located in a cryogenic cooling system, for example, to providecoupling to quantum hardware 502.

FIG. 6 depicts an example quantum computing system 600 according toexample embodiments of the present disclosure. The quantum computingsystem 600 can include one or more classical processors 602 and quantumhardware 604 including one or more qubits. The quantum computing system600 can include a chamber mount 608 configured to support the quantumhardware 604 and a vacuum chamber configured to receive the chambermount 608 and dispose the quantum hardware 604 in a vacuum. The vacuumchamber can form a cooling gradient from an end of the vacuum chamber(e.g., cap 607) to the quantum hardware 604. For example, the vacuumchamber can form a cooling gradient from a first temperature, such asroom temperature (e.g., about 300 Kelvin) to a second temperature, suchas at or about absolute zero (e.g., about 20 milliKelvin), such as toprovide a temperature at the quantum hardware 604 at which the qubitsexperience superconductivity. In some embodiments, the cooling gradientcan be formed by a plurality of cooling stages having progressivelyincreasing and/or decreasing temperatures. As one example, the coolingstages can be stages of a staged cryogenic cooling system, such as adilution refrigerator.

The quantum computing system 600 can include one or more signal linesbetween the classical processor(s) 602 and quantum hardware 604.According to example aspects of the present disclosure, the quantumcomputing system 600 can include one or more flex circuit boards 606including one or more signal lines. The flex circuit board(s) 606 can beconfigured to transmit signals by the one or more signal lines throughthe vacuum chamber to couple the one or more classical processors 602 tothe quantum hardware 604. The flex circuit board(s) 606 can include aplurality of signal lines and can provide a significantly improvedsignal line density, in addition to providing improved isolation,reduced thermal conductivity, and/or improved scalability. For instance,including flex circuit boards 606 according to example aspects of thepresent disclosure to couple the classical processors 602 to the quantumhardware 604 can provide for infrastructure that reliably scales to theincreasingly greater numbers of qubits that are achieved and/or expectedin contemporary and/or future quantum computing systems.

In some embodiments, some or all of the flex circuit board(s) 606 caninclude at least one ground layer. The ground layer can form an outersurface of the flex circuit board 606, such as an outer surface alongthe largest surface. In some embodiments, the flex circuit board 606 caninclude two ground layers, such as two parallel and spaced apart groundlayers. For instance, the two ground layers can form both largest outersurfaces of the flex circuit board 606. A ground layer can act as anelectrical isolation layer to isolate signal lines on one side of theground layer from interfering signals (e.g., from signal lines on otherlayers, other boards, the environment, etc.) on another side of theground layer. For instance, the ground layer can be coupled to earthground and/or other suitable ground(s).

The ground layer(s) can be or can include any suitable electricallyconductive material. In some embodiments, the ground layer(s) can be orcan include superconducting ground layer(s) including superconductingmaterial(s), such as superconducting material(s) that achieve(s)superconductivity at a temperature less than about 3 Kelvin, such asless than about 1 Kelvin, such as less than about 20 milliKelvin. Asexamples, the ground layer(s) can be or can include niobium, tin,aluminum, molybdenum disulfide, BSCCO, and/or other suitablesuperconducting materials. Additionally and/or alternatively, the groundlayer(s) can be or can include material having high signal transferperformance characteristics, such as low resistance, low reflectivity,low distortion, etc. such that a signal is substantially unchanged bypassing through the signal line. As examples, the ground layer(s) can beor can include copper, gold, and/or other suitable materials having highsignal transfer performance characteristics. Additionally and/oralternatively, the ground layer(s) can be or can include material(s)having desirable thermal characteristics, such as suitably high and/orlow thermal transfer, such as, for example, copper, copper alloy, thinsuperconducting materials, etc.

In some embodiments, the flex circuit board 606 can include at least onedielectric layer. The dielectric layer(s) can be or can include anysuitable dielectric material, such as dielectric polymers. In someembodiments, the dielectric layer(s) can be or can include flexibledielectric material. As one example, the dielectric layer(s) can be orcan include polyimide. At least a portion of the dielectric layer(s) canbe formed on or otherwise disposed proximate to at least a portion of aninner surface of the ground layer(s). For example, in some embodiments,an inner surface of a ground layer can be mated with an outer surface ofa dielectric layer. Furthermore, in some embodiments, inner surfaces oftwo dielectric layers can be mated with signal lines disposedtherebetween.

The flex circuit board 606 can include one or more signal lines. The oneor more signal lines can be disposed on a surface (e.g., an innersurface) of at least one dielectric layer. As an example, in someimplementations, the one or more signal lines can be disposed betweenopposing inner surfaces of two dielectric layers. The signal line(s) canbe or can include any suitable electrically conductive material. In someembodiments, the signal line(s) can be or can include superconductingsignal line(s) including superconducting material(s), such assuperconducting material(s) that achieve(s) superconductivity at atemperature less than about 3 Kelvin, such as less than about 1 Kelvin,such as less than about 20 milliKelvin. As examples, the signal line(s)can be or can include niobium, tin, aluminum, molybdenum disulfide,BSCCO, and/or other suitable superconducting materials. Additionallyand/or alternatively, the signal line(s) can be or can include materialhaving high signal transfer performance characteristics. As examples,the signal line(s) can be or can include copper, gold, and/or othersuitable materials having high signal transfer performancecharacteristics. Additionally and/or alternatively, the signal line(s)can be or can include material(s) having desirable thermalcharacteristics, such as, for example, copper, copper alloy, thinsuperconducting material, etc.

In some embodiments, the flex circuit board 606 can include one or morevias. For instance, the vias can extend through the ground layer(s), thedielectric layer(s), and/or the signal line(s). The vias can serve toimprove isolation of the signal lines. In some embodiments, the via(s)can be plated with via plate(s) that extend along the via(s). In someembodiments, the via plate(s) can be or can include conductive material,such as copper.

For instance, in some embodiments, a quantum computing system 600 caninclude quantum hardware 604 in data communication with one or moreclassical processor(s) 602. For instance, quantum hardware 604 canrepresent and/or manipulate information using qubits. A qubit can be orinclude any suitable quantum device that enables the superposition ofmultiple states, e.g., both the “0” and “1” state. As one example, aqubit can be or include a unit of superconducting material, such assuperconducting material that achieves superconductivity at atemperature less than about 3 Kelvin, such as less than about 1 Kelvin,such as less than about 20 milliKelvin. In some embodiments, the quantumcomputing system 600 can include one or more multi-level quantumsubsystems, such as a register of qubits. In some implementations, themulti-level quantum subsystems can include superconducting qubits, suchas flux qubits, charge qubits, transmon qubits, gmon qubits, etc.

The classical processor(s) 602 can be binary processors, such asprocessors that operate on data represented as a plurality of bits. Asone example, bits can be represented by a voltage differential between alow voltage (e.g., 0V) and a high voltage (e.g., 5V) at a point ofreference, such as a memory cell, circuit node, etc. The low voltage canbe associated with a “0” state and the high voltage can be associatedwith a “1” state. The classical processor(s) 602 can be configured to,in addition to any other suitable function(s) of the classicalprocessor(s) 602, control the quantum hardware 604. For instance, theclassical processor(s) 602 can be coupled to the quantum hardware 604(e.g., by signal lines included in flex circuit boards 606 according toexample aspects of the present disclosure) and/or configured to sendcontrol signals to perform quantum operations using the quantum hardware604. As one example, the classical processor(s) 602 can be configured tosend control signals that implement quantum gate operations at thequantum hardware 604 (e.g., by control device(s)). Additionally and/oralternatively, the classical processor(s) 602 can be configured to sendcontrol signals that cause the quantum hardware 604 to perform quantumstate measurements and/or provide the quantum state measurements to theclassical processor(s) 602 (e.g., by readout device(s)). For example,the classical processor(s) 602 can receive measurements of the quantumsystem that can be interpretable by the classical processor(s) 602.

According to example aspects of the present disclosure, the quantumcomputing system 600 can include one or more flex circuit boards 606including one or more signal lines. The classical processor(s) 602 canbe coupled to at least one first flex circuit board. For instance, theclassical processor(s) 602 can be coupled to the first flex circuitboard(s) 614 by a classical-flex interconnect 632. The classical-flexinterconnect 632 can convert from a classical signal transmission medium(e.g., a coaxial cable) 612 to the first flex circuit board(s) 614.

As one example, the classical-flex interconnect 632 can be or caninclude a compression interposer. The compression interposer can includean array (e.g., a two-dimensional array) of spring pads. A connectorreceiving signals from the classical processor(s) 602, such as via oneor more coaxial cables 612 (e.g., one coaxial cable 612 per signal line)can be compressed against the compression interposer to form signalcommunications between the spring pads and the connector (e.g., thecoaxial cables). The spring pads can each be coupled to a signal line onthe first flex circuit board 614 such that signals can be transmittedfrom the classical processor(s) 602 (e.g., the coaxial cables) to thesignal lines. The compression interposer can provide for connectingsignal transmission media 612 having a relatively lower spatial density,such as coaxial cables, which may occupy a relatively larger amount ofspace per cable, to signal transmission media having a relatively higherspatial density, such as signal lines embedded in a first flex circuitboard 614 provided according to example aspects of the presentdisclosure. Additionally, the compression interposer can achieve highisolation between signal lines and/or low reflectivity along a signalline that is/are suitable for quantum computing applications.

In some embodiments, the first flex circuit board(s) 614 can be or caninclude a first flex circuit board material at the ground layer(s)and/or the signal line(s). The first flex circuit board material can beselected to provide high signal transfer performance characteristics. Asexamples, the first flex circuit board material can be or can includecopper, brass, gold, and/or other suitable materials having high signaltransfer performance characteristics. For instance, the first flexcircuit board(s) 614 can include copper signal lines and/or groundlayer(s) to provide high signal transfer performance characteristics.

The first flex circuit board(s) 614 can pass through a hermetic seal 652positioned at an end (e.g., an entrance) of the vacuum chamber, such ascap 607. For example, a flex circuit board (e.g., first flex circuitboard 614) can be configured to pass through the hermetic seal 652 suchthat a first portion of the flex circuit board (e.g., first flex circuitboard 614) is disposed in the vacuum chamber and a second portion of theflex circuit board (e.g., first flex circuit board 614) is disposedoutside of the vacuum chamber while the hermetic seal 652 forms a vacuumseal for the vacuum chamber. The hermetic seal 652 can provide for thefirst flex circuit board(s) 614 to enter the vacuum chamber without(e.g., substantially) destroying a vacuum created by the vacuum chamber.As one example, the hermetic seal 652 can include a fitted seal for eachfirst flex circuit board 614. The fitted seal(s) can receive the firstflex circuit board(s) 614 and form a vacuum seal with surface(s) of thefirst flex circuit board(s) 614. Additionally, the hermetic seal 652 caninclude one or more seal slots configured to receive the fitted seal(s)and/or the first flex circuit board(s) 614. For example, the fittedseal(s) can form a vacuum seal with the seal slot(s) while allowing thefirst flex circuit board(s) 614 to pass through the seal slot(s) andinto the vacuum chamber. In this way, the flex circuit board(s) 606 canenter the vacuum chamber without experiencing signal disruptions frombreaks in the circuit boards, as the boards can continuously pass intothe vacuum chamber. In some embodiments, the hermetic seal 652 caninclude fastening systems to secure the fitted seals to the seal slotsand/or form a vacuum seal, such as, for example, screws, bolts, sealrings, O rings, etc. In some embodiments, the hermetic seal 652 can forma vacuum seal without requiring adhesive material (e.g., glue, resin,etc.) such that, for example, residual adhesive material does notcontaminate the flex circuit boards 606.

The first flex circuit board(s) 614 can be coupled to at least onesecond flex circuit board(s) 616. The first flex circuit board(s) 614can be coupled to the second flex circuit board(s) 616 by at least oneflex-flex interconnect 634. For instance, the flex-flex interconnect(s)634 can couple (structurally and/or electrically) the ground layer(s),dielectric layer(s), and/or signal line(s) of a first flex circuit board614 to a second flex circuit board 616. As examples, the flex-flexinterconnect(s) 634 can be formed by soldering, welding, and/orotherwise fusing components of a first flex circuit board 614 to asecond flex circuit board 616. The flex-flex interconnect(s) 634 can beor can include any suitable interconnection of two flex circuit board(s)606 such as, for example, a butt joint, an overlap joint, and/or anyother suitable interconnection(s). For instance, example flex-flexinterconnects that may be employed according to example aspects of thepresent disclosure is illustrated in FIG. 1 .

The second flex circuit board(s) 616 can have at least a differentmaterial composition from the first flex circuit board(s) 614. In someembodiments, the second flex circuit board(s) 616 can be or can includea second flex circuit board material at the ground layer(s) and/or thesignal line(s). The second flex circuit board material can be selectedto provide high signal transfer performance characteristics and/orreduced thermal conductivity. As examples, the second flex circuit boardmaterial can be or can include a copper alloy and/or other suitablematerials having desirable thermal characteristics. For instance, thesecond flex circuit board(s) 616 can include copper alloy signal linesand/or ground layer(s) to provide reduced thermal conductivity from theupper portions of the vacuum chamber (e.g., first circuit boards 614)and/or dispelling heat produced at subsequent components, such assurface mount attenuators 654.

In some embodiments, the second flex circuit board(s) 616 can be coupledto at least one surface mount attenuator board 618. For instance, thesecond flex circuit board(s) 616 can be coupled to the surface mountattenuator board(s) 618 by at least one flex-flex interconnect 636. Forinstance, the flex-flex interconnect(s) 636 can couple (structurallyand/or electrically) the ground layer(s), dielectric layer(s), and/orsignal line(s) of a second flex circuit board 616 to a surface mountattenuator board 618. As examples, the flex-flex interconnect(s) 636 canbe formed by soldering, welding, and/or otherwise fusing components of asecond flex circuit board 616 to a surface mount attenuator board 618.The flex-flex interconnect(s) 636 can be or can include any suitableinterconnection of two flex circuit board(s) 606 such as, for example, abutt joint, an overlap joint, and/or any other suitableinterconnection(s). For instance, example flex-flex interconnects thatmay be employed according to example aspects of the present disclosureis illustrated in FIG. 1 .

The surface mount attenuator board 618 can be a flexible printed circuitboard. In some embodiments, the surface mount attenuator board(s) 618can be or can include a surface mount attenuator board material at theground layer(s) and/or the signal line(s). The surface mount attenuatorboard material can be selected to provide high signal transferperformance characteristics. As examples, the surface mount attenuatorboard material can be or can include copper, brass, gold, and/or othersuitable materials having high signal transfer performancecharacteristics. For instance, the surface mount attenuator board caninclude copper signal lines and/or ground layer(s) to provide highsignal transfer performance characteristics.

The surface mount attenuator board(s) 618 can include one or moresurface mount attenuators 654. The surface mount attenuator(s) 654 canbe configured to attenuate or block thermal photon interference. In someembodiments, the surface mount attenuator board(s) 618 and/or thesurface mount attenuator(s) 654 can be placed at a temperature coldenough such that the surface mount attenuator(s) 654 do not producethermal photons. In some embodiments, the surface mount attenuator(s)654 can be disposed in an isolation plate. The isolation plate can beconfigured to isolate the one or more surface mount attenuators. Theisolation plate can be attached to the surface mount attenuator board(s)618. In some embodiments, the isolate plate can be mounted to a groundlayer and/or grounded. The isolation plate can include one or morecavities configured to isolate a first surface mount attenuator from asecond surface mount attenuator. For example, the cavities can surroundthe first surface mount attenuator in a direction of a second surfacemount attenuator and block cross-talk between attenuators.

The quantum computing system 600 can include at least one third flexcircuit board 620. For instance, the surface mount attenuator board(s)618 can be coupled to the third flex circuit board(s) 620 by at leastone flex-flex interconnect 638. For instance, the flex-flexinterconnect(s) 638 can couple (structurally and/or electrically) theground layer(s), dielectric layer(s), and/or signal line(s) of a surfacemount attenuator board 618 to a third flex circuit board 620. Asexamples, the flex-flex interconnect(s) 638 can be formed by soldering,welding, and/or otherwise fusing components of a surface mountattenuator board 618 to a third flex circuit board 620. The flex-flexinterconnect(s) 638 can be or can include any suitable interconnectionof two flex circuit board(s) 606 such as, for example, a butt joint, anoverlap joint, and/or any other suitable interconnection(s). Forinstance, example flex-flex interconnects that may be employed accordingto example aspects of the present disclosure is illustrated in FIG. 1 .

The third flex circuit board(s) 620 can be positioned at a point in thevacuum chamber at which the cooling gradient is cool enough such thatsome materials exhibit superconductivity. For example, at least aportion of the third flex circuit board(s) 620 can have a temperature ofless than about 3 Kelvin.

In some embodiments, the third flex circuit board(s) 620 can be or caninclude a third flex circuit board material at the ground layer(s)and/or the signal line(s). The third flex circuit board(s) 620 materialcan be selected to be superconducting at a temperature which at least aportion of the third flex circuit board(s) 620 experiencessuperconductivity. As examples, the third flex circuit board(s) 620material can be or can include niobium, tin, aluminum, and/or othersuitable superconducting materials. For instance, the third flex circuitboard(s) 620 can include copper-plated niobium signal lines and/orground layer(s) to provide superconductivity. For instance, the copperplating on the copper-plated niobium board(s) can be useful ininterfacing with the superconducting niobium, which can provide forimproved signal transfer characteristics. In some embodiments, thecopper-plated niobium board(s) can be formed by first applying a layerof niobium, followed by a thin layer of copper to prevent the formationof oxides, then a thicker layer of copper.

In some embodiments, the third flex circuit board(s) 620 can be coupledto at least one fourth flex circuit board 622. The third flex circuitboard(s) 620 can be coupled to the fourth flex circuit board(s) 622 byat least one flex-flex interconnect 640. For instance, the flex-flexinterconnect(s) 640 can couple (structurally and/or electrically) theground layer(s), dielectric layer(s), and/or signal line(s) of a thirdflex circuit board 620 to a fourth flex circuit board 622. As examples,the flex-flex interconnect(s) 640 can be formed by soldering, welding,and/or otherwise fusing components of a third flex circuit board 620 toa fourth flex circuit board 622. The flex-flex interconnect(s) 640 canbe or can include any suitable interconnection of two flex circuitboard(s) 606 such as, for example, a butt joint, an overlap joint,and/or any other suitable interconnection(s). For instance, exampleflex-flex interconnects that may be employed according to exampleaspects of the present disclosure is illustrated in FIG. 1 .

The fourth flex circuit board(s) 622 can couple the third flex circuitboard(s) 620 to the quantum hardware 604. For example, a connector 642at an end of the fourth flex circuit board(s) 622 can attach to a portthat is in signal communication with the quantum hardware 604. As oneexample, the connector can be a T-joint connector, such as a T-jointconnector including superconducting materials (e.g., tin). Additionallyand/or alternatively, the connector 642 may be a planar spring array.

In some embodiments, the fourth flex circuit board(s) 622 can be or caninclude a fourth flex circuit board material at the ground layer(s)and/or the signal line(s). The fourth flex circuit board(s) 622 materialcan be selected to provide high signal transfer performancecharacteristics. As examples, the fourth flex circuit board(s) 622material can be or can include copper, brass, gold, and/or othersuitable materials having high signal transfer performancecharacteristics. For instance, the fourth flex circuit board(s) 622 caninclude copper signal lines and/or ground layer(s) to provide highsignal transfer performance characteristics. Additionally and/oralternatively, the fourth flex circuit board(s) 622 material can beselected to be superconducting at temperature which at least a portionof the fourth flex circuit board(s) 622 experience. As examples, thefourth flex circuit board(s) 622 material can be or can include niobium,tin, aluminum, and/or other suitable superconducting materials.

In some embodiments, the fourth flex circuit board(s) 622 can be or caninclude a filter 656, such as an XYZ and/or IR filter 656. For instance,the filter 656 can be configured to reduce effects of noise, thermalphotons, and/or other potential sources of interference. As one example,the filter 656 can include a cavity in the fourth flex circuit board(s)622 that is filled with a filter material, such as a particulatesuspension, to provide XYZ/IR filtering. In some examples, the filtermaterial can provide less attenuation to signals of a first frequencyand greater attenuation to signals of a second, higher frequency. Forinstance, some filter materials provide attenuation that increases in asubstantially monotonic fashion with increasing signal frequency for atleast a portion of a targeted frequency band. In some embodiments,aspects of the filter material can be configured for lowpass and/orbandpass operation.

In some embodiments, the filter 656 can be bounded by one or moreboundaries of a cavity within the fourth flex circuit board(s) 622(e.g., a cavity within the dielectric material). For instance, a cavitywithin the fourth flex circuit board(s) 622 can be filled with a filtermaterial (e.g., a magnetically loaded polymer). In some embodiments, thecavity can be filled (e.g., partially or completely) with filtermaterial via an access within the fourth flex circuit board(s) 622 whenthe filter material is in any pourable, injectable, and/or moldablestate (e.g., flowing particulates, soft/plasticized materials, gels,slurries, pastes, foams, uncured thermosets, softened/meltedthermoplastics, etc.). In some embodiments, the cavity can be filledwith the filter material in a substantially solid state (e.g., bypress-fitting into the cavity, etc.).

In an example, control pulses may be transmitted over one or more signallines. (e.g., signal line(s) 116, 126) For example, a control pulse canbe transmitted by one or more classical processors coupled to the signalline(s). The control pulse can be or can include classical (e.g.,binary) computer-readable signal data, such as a voltage signal, and/orsignals that are implementable by quantum computing devices.

In an example, a control pulse is transmitted to one or more quantumcomputing devices via signal line(s) For example, the control pulse canbe transmitted, by the signal line(s), through a plurality of cryogeniccooling stages. For instance, signal line(s) carrying the control pulsecan be progressively decreasing in temperature from the classicalprocessor(s) (e.g., at room temperature and/or a temperature on theorder of about 100 Kelvin) to the quantum computing device(s) (e.g., ata temperature less than about 3 Kelvin, such as less than about 1Kelvin, such as less than about 20 milliKelvin) and through a pluralityof cryogenic cooling stages.

In an example, a control pulse may be applied to perform at least onequantum operation based at least in part on a control pulse. As oneexample, in some embodiments, quantum operation(s) can be or can includeobtaining state measurement(s) of the quantum computing device(s). Forinstance, a control pulse can instruct the quantum computing device(s)to measure a quantum state and/or resolve the quantum state to a basisstate representation. Additionally, the measured quantum state can betransmitted (e.g., by signal lines) to the classical processor(s).

As another example, in some embodiments, the quantum operation(s) can beor can include implementing at least one quantum gate operation byand/or at the quantum computing device(s). For instance, the controlpulse can be descriptive of microwave pulses that are applied to thequantum computing device(s) (e.g., qubits) to perform quantum gatingoperations. Example quantum gating operations include, but are notlimited to, Hadamard gates, controlled-NOT (CNOT) gates,controlled-phase gates, T gates, multi-qubit quantum gates, couplerquantum gates, etc.

Implementations of the digital and/or quantum subject matter and thedigital functional operations and quantum operations described in thisspecification can be implemented in digital electronic circuitry,suitable quantum circuitry or, more generally, quantum computationalsystems, in tangibly-implemented digital and/or quantum computersoftware or firmware, in digital and/or quantum computer hardware,including the structures disclosed in this specification and theirstructural equivalents, or in combinations of one or more of them. Theterm “quantum computing systems” may include, but is not limited to,quantum computers/computing systems, quantum information processingsystems, quantum cryptography systems, or quantum simulators.

Implementations of the digital and/or quantum subject matter describedin this disclosure can be implemented as one or more digital and/orquantum computer programs, i.e., one or more modules of digital and/orquantum computer program instructions encoded on a tangiblenon-transitory storage medium for execution by, or to control theoperation of, data processing apparatus. The digital and/or quantumcomputer storage medium can be a machine-readable storage device, amachine-readable storage substrate, a random or serial access memorydevice, one or more qubits/qubit structures, or a combination of one ormore of them. Alternatively or in addition, the program instructions canbe encoded on an artificially-generated propagated signal that iscapable of encoding digital and/or quantum information (e.g., amachine-generated electrical, optical, or electromagnetic signal) thatis generated to encode digital and/or quantum information fortransmission to suitable receiver apparatus for execution by a dataprocessing apparatus.

The terms quantum information and quantum data refer to information ordata that is carried by, held, or stored in quantum systems, where thesmallest non-trivial system is a qubit, i.e., a system that defines theunit of quantum information. It is understood that the term “qubit”encompasses all quantum systems that may be suitably approximated as atwo-level system in the corresponding context. Such quantum systems mayinclude multi-level systems, e.g., with two or more levels. By way ofexample, such systems can include atoms, electrons, photons, ions orsuperconducting qubits. In many implementations the computational basisstates are identified with the ground and first excited states, howeverit is understood that other setups where the computational states areidentified with higher level excited states (e.g., qudits) are possible.

The term “data processing apparatus” generally refers to digital and/orquantum data processing hardware and encompasses all kinds ofapparatuses, devices, and machines for processing digital and/or quantumdata, including by way of example a programmable digital processor, aprogrammable quantum processor, a digital computer, a quantum computer,or multiple digital and quantum processors or computers, andcombinations thereof. The apparatus can also be, or further include,special purpose logic circuitry, e.g., an FPGA (field programmable gatearray), or an ASIC (application-specific integrated circuit), or aquantum simulator, i.e., a quantum data processing apparatus that isdesigned to simulate or produce information about a specific quantumsystem. In particular, a quantum simulator is a special purpose quantumcomputer that does not have the capability to perform universal quantumcomputation. The apparatus can optionally include, in addition tohardware, code that creates an execution environment for digital and/orquantum computer programs, e.g., code that constitutes processorfirmware, a protocol stack, a database management system, an operatingsystem, or a combination of one or more of them.

A digital computer program, which may also be referred to or describedas a program, software, a software application, a module, a softwaremodule, a script, or code, can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a digital computing environment. A quantum computerprogram, which may also be referred to or described as a program,software, a software application, a module, a software module, a script,or code, can be written in any form of programming language, includingcompiled or interpreted languages, or declarative or procedurallanguages, and translated into a suitable quantum programming language,or can be written in a quantum programming language, e.g., QuantumComputation Language (QCL), Quipper, Cirq, etc.

A digital and/or quantum computer program may, but need not, correspondto a file in a file system. A program can be stored in a portion of afile that holds other programs or data, e.g., one or more scripts storedin a markup language document, in a single file dedicated to the programin question, or in multiple coordinated files, e.g., files that storeone or more modules, sub-programs, or portions of code. A digital and/orquantum computer program can be deployed to be executed on one digitalor one quantum computer or on multiple digital and/or quantum computersthat are located at one site or distributed across multiple sites andinterconnected by a digital and/or quantum data communication network. Aquantum data communication network is understood to be a network thatmay transmit quantum data using quantum systems, e.g. qubits. Generally,a digital data communication network cannot transmit quantum data,however a quantum data communication network may transmit both quantumdata and digital data.

The processes and logic flows described in this specification can beperformed by one or more programmable digital and/or quantum computers,operating with one or more digital and/or quantum processors, asappropriate, executing one or more digital and/or quantum computerprograms to perform functions by operating on input digital and quantumdata and generating output. The processes and logic flows can also beperformed by, and apparatus can also be implemented as, special purposelogic circuitry, e.g., an FPGA or an ASIC, or a quantum simulator, or bya combination of special purpose logic circuitry or quantum simulatorsand one or more programmed digital and/or quantum computers.

For a system of one or more digital and/or quantum computers orprocessors to be “configured to” or “operable to” perform particularoperations or actions means that the system has installed on itsoftware, firmware, hardware, or a combination of such that in operationcause the system to perform the operations or actions. For one or moredigital and/or quantum computer programs to be configured to performparticular operations or actions means that the one or more programsinclude instructions that, when executed by digital and/or quantum dataprocessing apparatuses, cause such apparatuses to perform the operationsor actions. A quantum computer may receive instructions from a digitalcomputer that, when executed by the quantum computing apparatus, causethe apparatus to perform the operations or actions.

Digital and/or quantum computers suitable for the execution of a digitaland/or quantum computer program can be based on general or specialpurpose digital and/or quantum microprocessors or both, or any otherkind of central digital and/or quantum processing unit. Generally, acentral digital and/or quantum processing unit will receive instructionsand digital and/or quantum data from a read-only memory, or a randomaccess memory, or quantum systems suitable for transmitting quantumdata, e.g. photons, or combinations thereof.

Some example elements of a digital and/or quantum computer are a centralprocessing unit for performing or executing instructions and one or morememory devices for storing instructions and digital and/or quantum data.The central processing unit and the memory can be supplemented by, orincorporated in, special purpose logic circuitry or quantum simulators.Generally, a digital and/or quantum computer will also include, or beoperatively coupled to receive digital and/or quantum data from ortransfer digital and/or quantum data to, or both, one or more massstorage devices for storing digital and/or quantum data, e.g., magnetic,magneto-optical disks, or optical disks, or quantum systems suitable forstoring quantum information. However, a digital and/or quantum computerneed not have such devices.

Digital and/or quantum computer-readable media suitable for storingdigital and/or quantum computer program instructions and digital and/orquantum data include all forms of non-volatile digital and/or quantummemory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks; and quantumsystems, e.g., trapped atoms or electrons. It is understood that quantummemories are devices that can store quantum data for a long time withhigh fidelity and efficiency, e.g., light-matter interfaces where lightis used for transmission and matter for storing and preserving thequantum features of quantum data such as superposition or quantumcoherence.

Control of the various systems described in this specification, orportions of them, can be implemented in a digital and/or quantumcomputer program product that includes instructions that are stored onone or more non-transitory machine-readable storage media, and that areexecutable on one or more digital and/or quantum processing devices. Thesystems described in this specification, or portions of them, can eachbe implemented as an apparatus, method, or electronic system that mayinclude one or more digital and/or quantum processing devices and memoryto store executable instructions to perform the operations described inthis specification.

While this disclosure contains many example implementation details,these should not be construed as limitations on the scope of what may beclaimed, but rather as descriptions of features that may be specific toparticular implementations. Certain features that are described inexamples of this disclosure in the context of separate implementationscan also be implemented in combination in a single implementation.Conversely, various features that are described in the context of asingle implementation can also be implemented in multipleimplementations separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various system modulesand components in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Particular implementations of the subject matter have been described.Other implementations are within the scope of the following claims. Forexample, the actions recited in the claims can be performed in adifferent order and still achieve desirable results. As one example, theprocesses depicted in the accompanying figures do not necessarilyrequire the particular order shown, or sequential order, to achievedesirable results. In some cases, multitasking and parallel processingmay be advantageous.

What is claimed is:
 1. An interconnection for connecting a plurality offlex circuit boards, comprising: a first flex circuit board having afirst side and a second side opposite the first side; a second flexcircuit board having a third side and a fourth side opposite the thirdside; wherein the first flex circuit board and the second flex circuitboard are physically coupled to each other in an overlap joint in whicha portion of the second side of the first flex circuit board overlaps aportion of the third side of the flex circuit board; wherein the firstflex circuit board comprises: a first signal line; a first dielectriclayer; and a first via extending through the first dielectric layer atleast from the first signal line to the second side of the first flexcircuit board; wherein the second flex circuit board comprises: a secondsignal line; a second dielectric layer; and a second via extendingthrough the second dielectric layer at least from the second signal lineto the third side of the second flex circuit board; and wherein theinterconnection further comprises a signal pad structure positioned inthe overlap joint between the second side of the first flex circuitboard and the third side of the second flex circuit board andelectrically coupled to the first via and the second via wherein thefirst via and the second via are offset in the overlap joint; whereinthe first signal line and the second signal line comprise asuperconducting material that achieves superconductivity at atemperature of less than about 3 Kelvin.
 2. The interconnection of claim1, further comprising: a first signal pad of the first flex circuitboard that is electrically coupled to the first via, a second signal padof the second flex circuit board that is electrically coupled to thesecond via, and solder that electrically and physically couples thefirst signal pad to the second signal pad.
 3. The interconnection ofclaim 1, wherein the first signal pad and the second signal pad have acircular structure.
 4. The interconnection of claim 1, wherein the firstvia extends from the second side through to the first side.
 5. Theinterconnection of claim 1, wherein the second via extends from thefourth side through to the third side.
 6. The interconnection of claim1, wherein the first flex circuit board comprises a first ground layerand a second ground layer, wherein the second flex circuit boardcomprises a third ground layer and a fourth ground layer, wherein thesecond ground layer is coupled by one or more solder connections to thethird ground layer.
 7. The interconnection of claim 1, wherein thesecond flex circuit board mirrors the first flex circuit board.
 8. Theinterconnection of claim 1, wherein the interconnection comprises aplurality of ground pads disposed at least partially around the firstsignal pad.
 9. The interconnection of claim 1, wherein the first via andthe second via do not overlap in the overlap joint.
 10. Theinterconnection of claim 1, wherein the first signal line and the secondsignal line comprise niobium, tin, aluminum, molybdenum disulfide, orbismuth strontium calcium copper oxide (BSCCO).
 11. A method forproducing a flex circuit board interconnection, comprising: obtaining afirst flex circuit board, the first flex circuit board having a firstside and a second side, the first flex circuit board comprising a firstsignal line and a first via extending through a first dielectric atleast from the first signal line to the second side of the first flexcircuit board; obtaining a second flex circuit board, the second flexcircuit board having a third side and a fourth side, the second flexcircuit board comprising a second signal line and a second via extendingthrough a second dielectric at least from the second signal line to thethird side of the second flex circuit board; aligning the first flexcircuit board and the second flex circuit board such that a signal padstructure is positioned in an overlap joint between the second side ofthe first flex circuit board and the third side of the second flexcircuit board; and coupling the at least the first via and at least thesecond via at the signal pad structure such that the first via and thesecond via are offset; wherein the first signal line and the secondsignal line comprise a superconducting material that achievessuperconductivity at a temperature of less than about 3 Kelvin.
 12. Themethod of claim 11, wherein coupling at least the first via and thesecond via at the signal pad structure comprises coupling the first viaand the second via using solder.
 13. The method of claim 11, wherein thefirst via does not extend to the first side.
 14. The method of claim 11,wherein the first via extends from the second side through to the firstside.
 15. The method of claim 11, wherein the second via does not extendto the fourth side.
 16. The method of claim 11, wherein the second viaextends from the fourth side through to the third side.
 17. The methodof claim 11, further comprising coupling a ground layer of the firstflex circuit board to a ground layer of the second flex circuit boardvia a solder connection.